I dump with partials but prefer to fill the black to 2/3 at least. I've not had any issues.

If I have enough fresh I block open the toilet and let it transfer to the black (on my stick built, keeping the valve open keeps the water running). I do not empty the fresh though as I like to keep enough in it for emergency use.

Many folks don't bother dumping partials if they are going out again the next weekend, I've not done this as my trips are farther apart.

If there's a line, we have a sewage treatment [plant about 20 minutes away right next to the highway, I can stop on the way home and dump for 1$. Never seen another rv there, just don't breathe.

Hi: All... We use "The Geo method" to treat the grey/black tanks. After dumping add a solution of Calgon water softener, dishwasher detergent, and extra bleach if necessary. Seems to keep the scum buildup to a min. and keeps the tanks slippery and fresh. All basic laundry products.
Do a google search of the geo method for the recipe!!! Alf
escape artist N.S. of Lake Erie

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Quote Bugs Bunny..."Don't take life too seriously, none of us get out of it ALIVE"!!!
'10 Frontier CC. S.E. 4X4 Lng. Bed V6 '14 Escape 5.0TA
St.Thomas Ont.( Not the Virgin Islands)

Because I never know if there is going to be water when I stop, I usually travel with 1/3 of a tank of fresh water. Also handy for flushing after a pit stop along the road when there are no facilities available. Never had a problem with it "sloshing" while driving.

I've added flush systems to both the black & gray tanks, and use them when dumping if a threaded water supply is available at the dump station & there isn't a line.